1. Field of the Invention
This invention relates to a wood working machine of the composite working type including a plurality of working heads for different working operations and a table translation apparatus for such wood working machine.
2. Description of the Related Art
A wood working machine of the composite working type has been proposed by the inventor of the present invention and is disclosed in Japanese Utility Model Laid-Open Application No. Heisel 3-50402. In the wood working machine, a chain conveyor is installed on a bed extending long in the depthwise direction, that is, in the forward and backward directions. The chain conveyor similarly extends long in the depthwise direction and is located higher than the top face of the bed, and a piece of wood to be worked is transported forwardly and backwardly by the chain conveyor. A sliding table is mounted on the bed and slidably moves forwardly and backwardly in a gap between the bed and the chain conveyor along a rail provided on the base. A screw shaft is supported for rotation on the bed and extends horizontally in the forward and backward direction. When the screw shaft is rotated forwardly or reversely by a motor, the sliding table is driven to move forwardly or backwardly between the front end and the rear end of the rail. A pair of left and right columns stand on the sliding table, and a cross beam is supported horizontally on the columns. The cross beam extends in the leftward and rightward directions above and perpendicularly to the chain conveyor, and the cross beam and the left and right columns exhibit an arch-like configuration so as not to interfere with the chain conveyor. A pair of carriers are mounted for leftward and rightward sliding movement on a front face and a rear face of the cross beam. A plurality of working heads each having a router or a like element principally for cutting wood are mounted for upward and downward movement on the front side carrier, and another plurality of working heads each having a drill or a like element principally for drilling wood are mounted for upward and downward movement on the rear side carrier.
In the wood working machine, in order to move the working position for wood in the forward or backward direction, the screw shaft is rotated forwardly or backwardly by the motor to slidably move the sliding table forwardly or backwardly on the bed together with the cross beam and the left and right columns. On the other hand, in order to move the working position for wood leftwardly or rightwardly, the carriers are moved leftwardly or rightwardly on the beam.
With the wood working machine, however, although transportation of wood is performed efficiently by the chain conveyor, since the weights of the front and rear carriers, the large number of working heads and so forth are applied to the sliding table together with the weights of the left and right columns and the cross beam, a great driving force is required to slidably move the sliding table of the great weight. However, since the sliding movement of the sliding table is performed by rotation of the single screw shaft, the sliding table cannot be slidably moved rapidly. Further, since the sliding table is slidably moved forwardly and backwardly by the single screw shaft, the screw shaft has a great length as much and cannot be rotated at a high speed. In order to work a piece of wood compositely in various manners, relative movement between the wood and each working head is required to be performed rapidly and repetitively within a short distance, and since a low speed of rotation of the screw shaft results in low forward or backward movement of the working head, composite workings cannot be performed efficiently on the wood working machine. Further, an increase of the length of the screw shaft increases deflections of the screw shaft upon rotation, and in order to prevent such deflections upon rotation, some countermeasure such as to increase the diameter of the screw shaft or to provide a support for preventing deflections upon rotation must be taken. This results in requirement for a further high driving force and complicated structure.